It's more than 2,000 years old, but the Great Wall of China remains one of the
greatest wonders of the world, an engineering feat rarely matched in the 22
centuries since its construction began. Stretching 4,500 miles, from the
mountains of Korea to the Gobi Desert, it was first built to protect an
ancient Chinese empire from marauding tribes from the north. It is actually a
series of walls built and rebuilt by different dynasties over 1,000 years
while they often served the same purpose. It has also evolved into something far
greater -- a boon to trade and prosperity and ultimately a symbol of Chinese
ingenuity and will. If the great wall were built in a straight line, it
could stretch from Miami, Florida to the North Pole.